Control system for a redundant prime mover system

ABSTRACT

The present invention provides a control system for a redundant prime mover system to drive a machine having an engine coupled to the machine, and a motor/generator coupled to the machine and an electrical network connection. The controller operates the engine and the motor/generator in three or four operating modes. The first operating mode drives the machine with the engine. The second operating mode drives the machine with the motor/generator. The third operating mode drives the machine and the motor/generator with the engine such that the motor/generator generates electricity for delivery to the electrical network connection. Alternatively, the third operating mode drives the machine with both the engine and the motor/generator. This alternate operating mode can also be included as a fourth operating mode.

FIELD OF THE INVENTION

The present invention relates generally to the field of control systemsand, more particularly, to a control system for a redundant prime moversystem.

BACKGROUND OF THE INVENTION

Large shaft driven machines, such as compressors or pumps, are typicallydriven by a single prime mover, such as an electric motor or engine. Forexample, compressors on natural gas pipelines are typically driven by anengine or turbine that burns natural gas from the pipeline. In locationswhere electricity is readily available, the compressor may be driven byan electric motor.

Motor/generators have been added to engine or turbine driven compressorsto generate startup torque and to generate electricity from the excessoutput power generated by the engine or turbine when the powerrequirement of the compressor is less than the output power generated bythe engine or turbine. Such a system is designed to continuously operatethe engine or turbine at an optimal level during all seasons no matterwhat the power requirement of the compressor is. As a result, thissystem is not designed to selectively run the compressor in more thantwo operating modes. Moreover, the system is not designed to generateand sell electricity back to the electric utility.

Another system uses a hydraulic turbine, motor/generator and pumpcombination wherein the motor/generator drives the pump to pump waterinto a reservoir in one mode and when the water is removed from thereservoir, the water drives the hydraulic turbine which drives themotor/generator to generate electricity. Similarly, a gas turbine,motor/generator and compressor combination has been used in a twooperating mode system. The gas turbine drives the motor/generator togenerate electricity when the compressor is not used, and themotor/generator drives the compressor when the gas turbine is not used.These systems are not designed to selectively run the compressor in morethan two operating modes depending on various parameters.

Accordingly, there is a need for a redundant prime mover system thatprovides increased reliability, versatility and efficiency.

SUMMARY OF THE INVENTION

The present invention provides a control system for a redundant primemover system that can be operated in three or four different operatingmodes, which increases the reliability, versatility and efficiency ofthe system. The present invention includes an engine or turbine, amotor/generator and a machine, such as a compressor or pump. The fourdifferent operating modes are: driving the machine with the engine orturbine; driving the machine with the motor/generator; driving themachine and the motor/generator with the engine or turbine such that themotor/generator generates electricity; and driving the machine with boththe engine or turbine and the motor/generator in a load sharingarrangement. The system can be selectively switched between these modesdepending on one or more parameters. As a result, the present inventioncan be set to run in the most cost effective mode or can arbitrage theprice differences between electricity and the fuel used by the engine.

The present invention provides a method for controlling amotor/generator and an engine coupled to a machine. A first operatingmode, a second operating mode or a third operating mode is selectedbased on one or more parameters. The engine drives the machine wheneverthe first operating mode is selected. The motor/generator drives themachine whenever the second operating mode is selected. The enginedrives the machine and the motor/generator such that the motor/generatorgenerates electricity for delivery to an electrical network connectionwhenever the third operating mode is selected. Alternatively, both theengine and the motor/generator drive the machine whenever the thirdoperating mode is selected. This alternate operating mode can also beincluded as a fourth operating mode.

The present invention also provides an apparatus for controlling anengine and a motor/generator to drive a machine. The apparatus includesa processor, a memory communicably coupled to the processor, an enginecontrol interface communicably coupled to the processor, and amotor/generator control interface communicably coupled to the processor.The processor selects a first operating mode, a second operating mode ora third operating mode based on one or more parameters. The processorcontrols the engine via the engine control interface to drive themachine whenever the first operating mode is selected. The processorcontrols the motor/generator via the motor/generator control interfaceto drive the machine whenever the second operating mode is selected. Theprocessor controls the engine via the engine control interface and themotor/generator via the motor/generator control interface to drive themachine and the motor/generator with the engine such that themotor/generator generates electricity for delivery to an electricalnetwork connection whenever the third operating mode is selected.Alternatively, both the engine and the motor/generator drive the machinewhenever the third operating mode is selected. This alternate operatingmode can also be included as a fourth operating mode

Moreover, the present invention provides a computer program embodied ona computer readable medium for controlling a motor/generator and anengine coupled to a machine. The computer program includes a codesegment for selecting a first operating mode, a second operating mode ora third operating mode based on one or more parameters, a code segmentfor driving the machine with the engine whenever the first operatingmode is selected, a code segment for driving the machine with themotor/generator whenever the second operating mode is selected, and acode segment for driving the machine and the motor/generator with theengine such that the motor/generator generates electricity for deliveryto an electrical network connection whenever the third operating mode isselected. Alternatively, both the engine and the motor/generator drivethe machine whenever the third operating mode is selected. Thisalternate operating mode can also be included as a code segment toimplement a fourth operating mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and further advantages of the invention may be betterunderstood by referring to the following description in conjunction withthe accompanying drawings, in which:

FIG. 1 is a block diagram of a redundant prime mover system inaccordance with one embodiment of the present invention;

FIG. 2 is a block diagram of a control system for a redundant primemover system in accordance with one embodiment of the present invention;

FIG. 3 is a block diagram of a controller for a redundant prime moversystem in accordance with one embodiment of the present invention;

FIGS. 4A, 4B, 4C, 4D and 4E are flowcharts of a control process for aredundant prime mover system in accordance with one embodiment of thepresent invention;

FIG. 5 is a block diagram of a redundant prime mover system inaccordance with another embodiment of the present invention; and

FIG. 6 is a block diagram of a redundant prime mover system inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention and do not delimit the scope of theinvention. Although the present invention will be described in referenceto a control system for a dual drive compressor system, the presentinvention is applicable to any control system for driving a machine,such as a compressor or pump, with an engine, or turbine, and amotor/generator.

The present invention provides a control system for a redundant primemover system that can be operated in three or four different operatingmodes, which increases the reliability, versatility and efficiency ofthe system. The present invention includes an engine or turbine, amotor/generator and a machine, such as a compressor or pump. The fourdifferent operating modes are: driving the machine with the engine orturbine; driving the machine with the motor/generator; driving themachine and the motor/generator with the engine or turbine such that themotor/generator generates electricity; and driving the machine with boththe engine or turbine and the motor/generator in a load sharingarrangement. The system can be selectively switched between these modesdepending on one or more parameters. As a result, the present inventioncan be set to run in the most cost effective mode or can arbitrage theprice differences between electricity and the fuel used by the engine.

FIG. 1 is a block diagram of a redundant prime mover system 100 inaccordance with one embodiment of the present invention. The redundantprime mover system 100 includes a motor/generator 102 coupled to acompressor 104 with a first coupling 106 (also referred to as the“M/G-COMP Coupling”) and a engine or turbine 108 coupled to thecompressor 104 with a second coupling 110 (also referred to as the“E/T-COMP Coupling”). Couplings 106 and 110 can be a clutch, magneticcoupling, gearbox or other suitable device to selectivelyengage/disengage the shaft of the compressor or pump 104. The engine 108can be a variable speed engine. In one embodiment of the presentinvention, the engine 108 is oversized so that some amount ofelectricity can be generated using the motor/generator 102 even with thecompressor 104 is operating at peak load. In small to mediumapplications, the motor/generator 102, compressor 104 and engine orturbine 108 are typically mounted on a skid 112 to form a package thatcan be transported and set up more quickly and economically thanindividually installing components 102, 104, 106, 108 and 110 in thefield. As will be appreciated by those skilled in the art, otherequipment (not shown), such as coolers, cooler drivers, scrubbers andapplication specific devices, may be connected to the motor/generator102, compressor 104 or engine 108.

The motor/generator 102 is electrically connected to an electricalnetwork connection 114, which is used as a source of electricity to runthe motor/generator 102 and drive the compressor 104 and a deliverypoint for the electricity generated by the motor/generator 102 when theengine 108 is supplying more output power than is required to drive thecompressor 104. The exact interface between the electrical networkconnection 114 and the transmission or distribution system 116 will varyfrom one installation to another. One possible interface may include astep-down/step-up transformer 118 connected to the transmission ordistribution system line 116 via breaker 120. The step-down/step-uptransformer 118 can be isolated with switches 122 and 124. A meter 126records the energy flow to and from the step-down/set-up transformer118. Meter 126 is connected between the step-down/step-up transformer118 and the electrical network connection 114, and may be isolated withswitches 128 and 130 or bypassed with switch 132. Other metering andprotective devices may also be used, such as protective relays (notshown), lightning arrestors 134 and 136, potential transformers 138,etc.

Although a compressor 104 is depicted, compressor 104 could also be apump or other machine that is driven by large engines, turbines ormotors. Input line 140 and output line 142 are connected to compressor104. As will be appreciated by those skilled in the art, the connectionof the lines 140 and 142 to the compressor 104 will also include variousvalves, regulators and other flow protection/regulation devices. Theselines 140 and 142 may be taps off of a pipeline, such as natural gas orother petroleum product, or part of a processing plant. If input line140 contains a product that can be used as fuel for the engine orturbine 108, a first fuel supply line 144 having a regulating valve 146will connect the input line 140 to the engine or turbine 108. In suchcases, first fuel supply line 144 will serve as the primary fuel supplyfor the engine or turbine 108. A second fuel supply line 148 having aregulating valve 150 will typically connect the engine or turbine 108 toan alternate fuel supply. If input line 140 does not contains a productthat can be used as fuel for the engine or turbine 108, second fuelsupply line 148 will be the primary source of fuel to the engine orturbine 108.

Now referring to FIG. 2, a block diagram of a control system 200 for aredundant prime mover system in accordance with one embodiment of thepresent invention is shown. A controller 202 is communicably coupled tothe engine or turbine 108, the second coupling 110, the compressor 104,the first coupling 106 and the motor/generator 102. The controller 202monitors and controls the operation of these components 102, 104, 106,108 and 110. The controller 202 can be installed on the skid 112(FIG. 1) or in a remotely located control room or building (not shown).The controller 202 may also be communicably coupled to one or moreinput/output (“I/O”) devices 212 and data storage devices 204. Thesystem 200 can be controlled and monitored from the controller 202 orfrom a remote terminal 206 communicably coupled to the controller 202via a network 208 or a direct communication link (not shown). Thecontroller 202 can also send and retrieve data or commands from a remoteserver 210 communicably coupled to the controller 202 via network 208.

Referring now to FIG. 3, a block diagram of a controller 202 for aredundant prime mover system in accordance with one embodiment of thepresent invention is shown. The controller 202 includes one or moreprocessors 302 communicably coupled to a memory 304. Memory 304 can beread only memory (“ROM”) and/or random access memory (“RAM”). The one ormore processors 302 are communicably coupled to a engine controlinterface 306, a compressor control interface 308, a motor/generatorcontrol interface 310, an I/O interface 312 and a remote interface 314.The controller 202 controls and monitors the engine or turbine 108 (FIG.2) using the engine control interface 306. The second coupling 110 (FIG.2) can be controlled and monitored using engine control interface 306,the compressor interface 308 or a separate interface (not shown).Similarly, the controller 202 controls and monitors the motor/generator102 (FIG. 2) using the motor/generator control interface 310. The firstcoupling 106 (FIG. 2) can be controlled and monitored usingmotor/generator control interface 310, the compressor interface 308 or aseparate interface (not shown). The controller 202 controls and monitorsthe compressor 104 (FIG. 2) using the compressor control interface 308.Note that some or all of these three interfaces 306, 308 and 310 can becombined into a single interface. Moreover, each interface 306, 308 and310 can be individually wired connections. The I/O interface 312communicably couples the processor 320 to the I/O devices 202 (FIG. 2)and data storage devices 204 (FIG. 2). Similarly, the remote interface314 communicably couples the processor 320 to the remote terminal 206(FIG. 2) and data server 210 (FIG. 2). The I/O interface 312 and remoteinterface 314 can be a serial, parallel, universal serial bus (“USB”),Ethernet, telephone or other type of computer interface. As will beappreciated by those skilled in the art, the interfaces 306, 308, 310,312 and 314 include the necessary hardware, software and drivers toestablish communication between the processor and the connected devices.

Now referring to FIG. 4A, a flowchart of a control process 400 for aredundant prime mover system in accordance with one embodiment of thepresent invention is shown. The control process 400 starts in block 402and the system determines whether it is in manual or automatic mode indecision block 404. If the system is not in automatic mode, asdetermined in decision block 404, an operating mode is selected in block406. If the system is in automatic mode, as determined in decision block404, one or more parameters, such as operational data, are obtained andthe proper operating mode is determined in block 408. The one or moreparameters may include an estimated operational cost for the engine, anestimated operational cost for the motor/generator, a selling price forelectricity, a fuel cost for the engine, an electricity cost for themotor/generator, a time period, an emission limit, an audible noiselimit, or any other operational data.

Once the operating mode has been selected or determined in either block406 or block 408, and if the operating mode is new (initial operatingmode or different from the current operating mode), as determined indecision block 410, and if it is not time to re-determined the operatingmode, as determined in decision block 412, the system waits apredetermined amount of time in block 414 before it re-determines theoperating mode. If, however, it is time to re-determined the operatingmode, as determined in decision block 412, operating data is obtainedand the proper operating mode is determined in block 416. If the systemis set to automatic, as determined in decision block 418, the processloops back to decision block 410 to determine whether the re-determinedoperating mode is new. If, however, the system is not set to automatic,as determined in decision block 418, the system recommends that theoperating mode be changed in block 420 and then loops back to block 406where the operating mode is selected. If a new operating mode is notselected in block 406, the re-determination process can be repeated.

The control process 400 of the present invention operates themotor/generator 102 (FIGS. 1 and 2), compressor 104 (FIGS. 1 and 2) andengine 108 (FIGS. 1 and 2) in three or four operating modes. Theoperating modes can be selected manually or automatically. The firstoperating mode drives the machine with the engine. The second operatingmode drives the machine with the motor/generator. The third operatingmode drives the machine and the motor/generator with the engine suchthat the motor/generator generates electricity for delivery to theelectrical network connection. Alternatively, the third operating modedrives the machine with both the engine and the motor/generator. Thisalternate operating mode can also be included as a fourth operatingmode.

For example, the present invention can be set to operate in the mostcost efficient manner using three operating modes based on theseparameters: a first estimated operational cost for the engine, a secondestimated operational cost for the engine, an estimated operational costfor the motor/generator and a selling price for the electricity. Thefirst estimated operational cost for the engine corresponds to theoperating costs to drive the compressor 104 (FIGS. 1 and 2) with theengine 108 (FIGS. 1 and 2). The second estimated operational cost forthe engine corresponds to the incremental cost to drive the compressor104 (FIGS. 1 and 2) and the motor/generator 102 (FIGS. 1 and 2). Thefirst operating mode occurs whenever a first estimated operational costfor the engine 108 (FIGS. 1 and 2) is less than an estimated operationalcost for the motor/generator 102 (FIGS. 1 and 2). The second operatingmode occurs whenever an estimated operational cost for themotor/generator 102 (FIGS. 1 and 2) is less than or equal to the firstestimated operational cost for the engine 108 (FIGS. 1 and 2). The thirdoperating mode occurs whenever a selling price for the electricity isgreater than the second estimated operational cost for the engine 108(FIGS. 1 and 2). The processor 302 (FIG. 3) can calculate the firstoperational cost for the engine 108 (FIGS. 1 and 2), second operationalcost for the engine 108 (FIGS. 1 and 2), operational cost for themotor/generator 102 (FIGS. 1 and 2) and selling price for theelectricity using current and/or historical data. These operating modescan be manually controlled, preprogrammed, or determined in real-time,near real-time or from historical and/or projected data. For example,the operating modes could be triggered by selected time periods tooperate in the first operating mode during the summer months (excludingelectrical peaking periods), the second operating mode during theremaining months, and the third operating mode during the electricalpeaking periods.

If the operating mode is new (initial operating mode or different fromthe current operating mode), as determined in decision block 410, andthe new operating mode is the first operating mode, as determined indecision block 422, the E/T start process is executed in block 424. TheE/T start process 424 is described below in reference to FIG. 4B. Aftercompletion of the E/T start process in block 424, the process loops backto decision block 412 to determine whether it is time to re-determine orupdate the operating mode. If, however, the new operating mode is notthe first operating mode, as determined in decision block 422, and thenew operating mode is the second operating mode, as determined indecision block 426, the M/G start process is executed in block 428. TheM/G start process 428 is described below in reference to FIG. 4C. Aftercompletion of the M/G start process in block 428, the process loops backto decision block 412 to determine whether it is time to re-determine orupdate the operating mode. If, however, the new operating mode is notthe second operating mode, as determined in decision block 426, and thenew operating mode is the third operating mode, as determined indecision block 430, the generation start process is executed in block432. The generation start process 432 is described below in reference toFIG. 4D. After completion of the generation start process in block 432,the process loops back to decision block 412 to determine whether it istime to re-determine or update the operating mode. If, however, the newoperating mode is not the third operating mode, as determined indecision block 430, and the new operating mode is the fourth operatingmode, as determined in decision block 434, the load sharing startprocess is executed in block 436. The load sharing start process 436 isdescribed below in reference to FIG. 4E. After completion of the loadsharing start process in block 436, the process loops back to decisionblock 412 to determine whether it is time to re-determine or update theoperating mode. If, however, the new operating mode is not the fourthoperating mode, as determined in decision block 434, and the shut downprocess has not been ordered, as determined in decision block 438, aerror process will commence in block 440. The error process 440 mayinclude various system checks, diagnostics and reporting functions, andmay or may not initiate a shut down process or “safe” operating mode.If, however, the shut down process has been ordered, as determined indecision block 438, the shut down process will be executed in block 442and the process ends in block 444.

Referring now to FIG. 4B, a flowchart of the engine or turbine startprocess 424 of FIG. 4A for a redundant prime mover system in accordancewith one embodiment of the present invention is shown. The E/T startprocess 424 begins in block 450. If the engine or turbine 108 (FIG. 1)is not on, as determined in decision block 452, the engine or turbine108 (FIG. 1) is started in block 454. If the engine or turbine 108(FIG. 1) is not up to the proper speed to engage the E/T-COMP coupling110 (FIG. 1), as determined in decision block 456, and the start processhas not exceeded a specified period of time (“timed out”), as determinedin decision block 458, the process will wait in block 460 for a periodof time before the engine or turbine 108 (FIG. 1) speed is checked againin decision block 456. If, however, the start process has timed out, asdetermined in decision block 458, an error process will be initiated inblock 462. The error process 462 may include various system checks,diagnostics and reporting functions. The error process 462 may also shutthe engine or turbine 108 (FIG. 1) down and disable the E/T startprocess 424 and generation start process 432 until a technician servicesthe control system and the engine or turbine 108 (FIG. 1). If the engineor turbine 108 (FIG. 1) is up to the proper speed, as determined indecision block 456, the E/T-COMP coupling 110 (FIG. 1) is engaged inblock 464. If the motor/generator 102 (FIG. 1) is not on, as determinedin decision block 466, the system suspends further processing until atransition delay period has expired in block 468 and the process returnsin block 470. The transition delay period can be a minimum time to runthe engine or turbine 108 (FIG. 1) in the first operating mode based onthe costs and equipment wear and tear associated with changing operatingmodes. For example, the system may be specified to prevent changingoperating modes every few minutes or even every hour. Alternatively,there may be a maximum number of changes allowed per day, week or month.

If, however, the motor/generator 102 (FIG. 1) is on, as determined indecision block 466, the M/G-COMP coupling 106 (FIG. 1) is disengaged inblock 472 and the motor/generator 102 (FIG. 1) is shut down in block474. As before, the system suspends further processing until thetransition delay period has expired in block 468 and returns to the mainprocess (FIG. 4) in block 470. If, however, the engine or turbine 108(FIG. 1) is on, as determined in decision block 452, and themotor/generator 102 (FIG. 1) is not on, as determined in decision block476, the process returns in block 470 to the main process (FIG. 4)because the system is already in the first operating mode. If, however,the motor/generator 102 (FIG. 1) is on, as determined in decision block476, the M/G-COMP coupling 106 (FIG. 1) is disengaged in block 478 andthe motor/generator 102 (FIG. 1) is shut down in block 480. The speed ofthe engine or turbine 108 (FIG. 1) is reduced in block 482 to only drivethe compressor instead of both the compressor and motor/generator. Thesystem suspends further processing until the transition delay period hasexpired in block 468 and returns in block 470 to the main process (FIG.4).

Now referring to FIG. 4C, a flowchart of the motor/generator startprocess 428 of FIG. 4A for a redundant prime mover system in accordancewith one embodiment of the present invention is shown. The M/G startprocess 428 begins in block 490. If the motor/generator 102 (FIG. 1) isnot on, as determined in decision block 492, the motor/generator 102(FIG. 1) is started in block 494. If the motor/generator 102 (FIG. 1) isnot up to the proper speed to engage the M/G-COMP coupling 106 (FIG. 1),as determined in decision block 496, and the start process has not timedout, as determined in decision block 498, the process will wait in block500 for a period of time before the motor/generator 102 (FIG. 1) speedis checked again in decision block 496. If, however, the start processhas timed out, as determined in decision block 498, an error processwill be initiated in block 502. The error process 502 may includevarious system checks, diagnostics and reporting functions. The errorprocess 502 may also shut the motor/generator 102 (FIG. 1) down anddisable the M/G start process 428 and generation start process 432 untila technician services the control system and the motor/generator 102(FIG. 1). If the motor/generator 102 (FIG. 1) is up to the proper speed,as determined in decision block 496, the M/G-COMP coupling 106 (FIG. 1)is engaged in block 504. If the motor/generator 102 (FIG. 1) is not on,as determined in decision block 506, the system suspends furtherprocessing until a transition delay period has expired in block 508 andthe process returns in block 510. The transition delay period can be aminimum time to run the motor/generator 102 (FIG. 1) in the firstoperating mode based on the costs and equipment wear and tear associatedwith changing operating modes. For example, the system may be specifiedto prevent changing operating modes every few minutes or even everyhour. Alternatively, there may be a maximum number of changes allowedper day, week or month.

If, however, the motor/generator 102 (FIG. 1) is on, as determined indecision block 506, the E/T-COMP coupling 110 (FIG. 1) is disengaged inblock 512 and the engine or turbine 108 (FIG. 1) is shut down in block514. As before, the system suspends further processing until thetransition delay period has expired in block 508 and returns to the mainprocess (FIG. 4) in block 510. If, however, the motor/generator 102(FIG. 1) is on, as determined in decision block 492, and the engine orturbine 108 (FIG. 1) is not on, as determined in decision block 516, theprocess returns in block 510 to the main process (FIG. 4) because thesystem is already in the second operating mode. If, however, the engineor turbine 108 (FIG. 1) is on, as determined in decision block 516, thespeed of the engine or turbine 108 (FIG. 1) is reduced in block 518 sothat the system is not generating electricity. The E/T-COMP coupling 110(FIG. 1) is disengaged in block 520 and the engine or turbine 108(FIG. 1) is shut down in block 522. The system suspends furtherprocessing until the transition delay period has expired in block 508and returns in block 510 to the main process (FIG. 4).

Referring now to FIG. 4D, a flowchart of the generation start process432 of FIG. 4A for a redundant prime mover system in accordance with oneembodiment of the present invention is shown. The generation startprocess 432 begins in block 530. If the engine or turbine 108 (FIG. 1)is not on, as determined in decision block 532, the engine or turbine108 (FIG. 1) is started in block 534. If the engine or turbine 108(FIG. 1) is not up to the proper speed to engage the E/T-COMP coupling110 (FIG. 1), as determined in decision block 536, and the start processhas not timed out, as determined in decision block 538, the process willwait in block 540 for a period of time before the engine or turbine 108(FIG. 1) speed is checked again in decision block 536. If, however, thestart process has timed out, as determined in decision block 538, anerror process will be initiated in block 542. The error process 542 mayinclude various system checks, diagnostics and reporting functions. Theerror process 542 may also shut the engine or turbine 108 (FIG. 1) downand disable the E/T start process 424, generation start process 432 andload sharing start process 436 until a technician services the controlsystem and the engine or turbine 108 (FIG. 1). If the engine or turbine108 (FIG. 1) is up to the proper speed, as determined in decision block536, the E/T-COMP coupling 110 (FIG. 1) is engaged in block 544. If themotor/generator 102 (FIG. 1) is on, as determined in decision block 546,the speed of the engine or turbine 108 (FIG. 1) is increased in block548 so that the system generates electricity. The system suspendsfurther processing until a transition delay period has expired in block550 and the process returns in block 552. The transition delay periodcan be a minimum time to run the motor/generator 102 (FIG. 1) and engineor turbine 108 (FIG. 1) in the third operating mode based on the costsand equipment wear and tear associated with changing operating modes.For example, the system may be specified to prevent changing operatingmodes every few minutes or even every hour. Alternatively, there may bea maximum number of changes allowed per day, week or month.

If, however, the motor/generator 102 (FIG. 1) is not on, as determinedin decision block 546, the motor/generator 102 (FIG. 1) is started inblock 554. If the motor/generator 102 (FIG. 1) is up to the properspeed, as determined in decision block 556, the M/G-COMP coupling 106(FIG. 1) is engaged in block 558 and the speed of the engine or turbine108 (FIG. 1) is increased in block 548 so that the system generateselectricity. The system suspends further processing until a transitiondelay period has expired in block 550 and the process returns in block552. If, however, the motor/generator 102 (FIG. 1) is not up to theproper speed to engage the M/G-COMP coupling 106 (FIG. 1), as determinedin decision block 556, and the start process has not timed out, asdetermined in decision block 560, the process will wait in block 562 fora period of time before the motor/generator 102 (FIG. 1) speed ischecked again in decision block 556. If, however, the start process hastimed out, as determined in decision block 560, an error process will beinitiated in block 564. The error process 564 may include various systemchecks, diagnostics and reporting functions. The error process 564 mayalso shut the motor/generator 102 (FIG. 1) down and disable the M/Gstart process 428, generation start process 432 and load sharing startprocess 436 until a technician services the control system and themotor/generator 102 (FIG. 1).

If, however, the engine or turbine 108 (FIG. 1) is on, as determined indecision block 532, and the motor/generator 102 (FIG. 1) is on, asdetermined in decision block 566, the process returns in block 552 tothe main process (FIG. 4) because the system is already in the thirdoperating mode. If, however, the motor/generator 102 (FIG. 1) is not on,as determined in decision block 566, the motor/generator 102 (FIG. 1) isstarted in block 554 and the process continues as previously described.

Referring now to FIG. 4E, a flowchart of the load sharing start process436 of FIG. 4A for a redundant prime mover system in accordance with oneembodiment of the present invention is shown. The load sharing startprocess 436 begins in block 570. If the engine or turbine 108 (FIG. 1)is not on, as determined in decision block 572, the engine or turbine108 (FIG. 1) is started in block 574. If the engine or turbine 108(FIG. 1) is not up to the proper speed to engage the E/T-COMP coupling110 (FIG. 1), as determined in decision block 576, and the start processhas not timed out, as determined in decision block 578, the process willwait in block 580 for a period of time before the engine or turbine 108(FIG. 1) speed is checked again in decision block 576. If, however, thestart process has timed out, as determined in decision block 578, anerror process will be initiated in block 582. The error process 582 mayinclude various system checks, diagnostics and reporting functions. Theerror process 582 may also shut the engine or turbine 108 (FIG. 1) downand disable the E/T start process 424, generation start process 432 andload sharing start process 436 until a technician services the controlsystem and the engine or turbine 108 (FIG. 1). If the engine or turbine108 (FIG. 1) is up to the proper speed, as determined in decision block576, the E/T-COMP coupling 110 (FIG. 1) is engaged in block 584. If themotor/generator 102 (FIG. 1) is on, as determined in decision block 586,the output of the engine or turbine 108 (FIG. 1) and motor/generator 102(FIG. 1) are adjusted to share the load of the compressor 104 in block588. The system suspends further processing until a transition delayperiod has expired in block 590 and the process returns in block 592.The transition delay period can be a minimum time to run themotor/generator 102 (FIG. 1) and engine or turbine 108 (FIG. 1) in thefourth operating mode based on the costs and equipment wear and tearassociated with changing operating modes. For example, the system may bespecified to prevent changing operating modes every few minutes or evenevery hour. Alternatively, there may be a maximum number of changesallowed per day, week or month.

If, however, the motor/generator 102 (FIG. 1) is not on, as determinedin decision block 586, the motor/generator 102 (FIG. 1) is started inblock 594. If the motor/generator 102 (FIG. 1) is up to the properspeed, as determined in decision block 596, the M/G-COMP coupling 106(FIG. 1) is engaged in block 598 and the speed of the engine or turbine108 (FIG. 1) and motor/generator 102 (FIG. 1) are adjusted to share theload of the compressor 104 in block 588. The system suspends furtherprocessing until a transition delay period has expired in block 590 andthe process returns in block 592. If, however, the motor/generator 102(FIG. 1) is not up to the proper speed to engage the M/G-COMP coupling106 (FIG. 1), as determined in decision block 596, and the start processhas not timed out, as determined in decision block 600, the process willwait in block 602 for a period of time before the motor/generator 102(FIG. 1) speed is checked again in decision block 596. If, however, thestart process has timed out, as determined in decision block 600, anerror process will be initiated in block 604. The error process 604 mayinclude various system checks, diagnostics and reporting functions. Theerror process 604 may also shut the motor/generator 102 (FIG. 1) downand disable the M/G start process 428, generation start process 432 andload sharing start process 436 until a technician services the controlsystem and the motor/generator 102 (FIG. 1).

If, however, the engine or turbine 108 (FIG. 1) is on, as determined indecision block 572, and the motor/generator 102 (FIG. 1) is on, asdetermined in decision block 606, the process returns in block 592 tothe main process (FIG. 4) because the system is already in the thirdoperating mode. If, however, the motor/generator 102 (FIG. 1) is not on,as determined in decision block 606, the motor/generator 102 (FIG. 1) isstarted in block 594 and the process continues as previously described.

The following data illustrates an example of some of the equipment thatcan be used to implement the present invention. The applicable data forcompressor 654 is:

Manufacturer: ARIEL Model: JGT-4 Configuration: No. of Throws: FOUR No.of Stages: ONE Speed Range Min/Max. RPM: 750/1500 Design Speed:1400/1180 Piston Speed-FPM: 1050/885 Elevat'n Ft: 1000 Barmtr Psia:14.165 Amb'nt Degf: 100 Compressor Data: Driver Data: Frame Model: Jgt/4Stroke Inch: 4.500 Rod Dia Inch: 2.000 Type: Gas Engine Max R1 # Tot:74000 Max R1 # Tens: 37000 Max R1 # Comp: 40000 Mfr: Caterpillar RatedRpm: 1500 Rated Bhp: 2600 Rated Ps Fpm: 1125 Model: 3516tale Calc Rpm:1400 Calc Bhp: 1150 Calc Ps Fpm: 1050 Bhp: 1265 (Cont) ServicesGathering Stage Data: Stage 1 Flow Req'd Mmscfd 15.000 Flow Calc Mmscfd13.991 Cyl Hp Per Stage 1131.2 Specific Gravity 0.6500 Ratio Of Sp Ht′N′ 1.2620 Comprsblty Suc Zs 0.9558 Comprsblty Dch Zd 0.9539 Pres SucLine Psig 250.00 Pres Suc Flg Psig 247.50

Pres Dch Flg Psig 959.50 Pres Dch Line Psig 950.0 Pres Ratio F/F 3.7210TEMP SUC Degf 80.0 TEMP CLF DCH Degf 120.0 Cylinder Data: Throw 1 Throw2 Throw 3 Throw 4 Cylinder Model 7-1/4t 7-1/4t 7-1/4t 7-1/4t CylinderBore Inch 7.250 7.250 7.250 7.250 Cyl Rdp (Api) Psig 1727.0 1727.01727.0 1727.0 Cylinder Mawp Psig 1900.0 1900.0 1900.0 1900.0 CylinderAction Dbl Dbl Dbl Dbl Cylinder Disp Cfm 289.564 289.564 289.564 289.564Pres Suc Intl Psig 226.98 226.98 226.98 226.98 TEMP SUC INTL Degf 86.9786.97 86.97 86.97 Cmprsb'y Suc Zsph 0.9576 0.9576 0.9576 0.9576 Pres DchIntl Psig 1035.46 1035.46 1035.46 1035.46 TEMP DCH INTL Degf 281.98281.98 281.98 281.98 He Suc Gas Vel Fpm 9267 9267 9267 9267 He Dch GasVel Fpm 8957 8957 8957 8957 He Spacrs Used/Max 0/4 0/4 0/4 0/4 He Vvpkt% Cl Avail 0.9 + 52.4 0.9 + 52.4 0.9 + 52.4 0.9 + 52.4 % Of Vvpkt Used19.19 19.19 19.19 19.19 He Min Clearance % 17.76 17.76 17.76 17.76 HeTot Clearance % 28.68 28.68 28.68 28.68 He Vol Eff % 40.57 40.57 40.5740.57 Ce Suc Gas Vel Fpm 8562 8562 8562 8562 Ce Dch Gas Vel Fpm 82768276 8276 8276 Ce Spacrs Used/Max 0/4 0/4 0/4 0/4 Ce Min Clearance %20.73 20.73 20.73 20.73 Ce Tot Clearance % 20.73 20.73 20.73 20.73 CeVol Eff % 54.94 54.94 54.94 54.94 Suc Pseu-Q He/Ce % 9.6/8.5 9.6/8.59.6/8.5 9.6/8.5 Gas Rod Ld Out # 34267 C 34267 C 34267 C 34267 C Gas RodLd In # 29968 T 29968 T 29968 T 29968 T Gas Rod Ld Tot # 64235 6423564235 64235 Gas Rod Ld Revrsl Yes Yes Yes Yes Flow Calc Mmscfd 3.4983.498 3.498 3.498 Cylinder 282.8 282.8 282.8 282.8The cylinders have manually adjustable VV pockets. Plate type valves areused. The compressor 104 also includes utility piping with a valve todrain crankcase oil to the edge of the skid 112. Packing vents anddrains are also piped to edge of the skid 112. Frame oil piping isinstalled as required.

The applicable data for the engine 108 is:

Manufacturer: CATERPILLAR Model: 3516TALE Configuration/No. ofCylinders: V-16 Combustion Type: Turbo-Charged Compression Ratio: 8:1Bore X Stroke: 6.7 × 7.5 Displacement (cu. inches): 4210 Speed RangeMin/Max: 900-1400 Continuous BHP @ Mfg. Rating: 1265 @ 1400 RPM 1180 @1300 RPM 1085 @ 1200 RPM  995 @ 1100 RPM

-   -   Ignition System: Caterpillar Electronic Ignition System        (E.I.S.).    -   Exhaust System: Residential Grade Muffler Mounted on Top of the        Cooler with a Stainless Steel Expansion Joint.    -   Fuel Gas System: Coalescing Fuel Gas Filter, Block Valve, Fuel        Shutoff and Vent Valve, Relief Valve, Pressure Regulators.    -   Starting System: Ingersoll Rand Starter with Strainer, Pre-Lube,        Push Button for Remote Start, Exhaust Piped to Top of Cooler.    -   Emissions: Nox 2.0 grams, CO 1.9 grams, NMHC 0.44 grams    -   Also Includes: Turbocharger oil accumulator to lubricate and        coal turbo system after shutdown.

The applicable data for the motor/generator 102 is:

BRAND: Teco-Westinghouse BHP: 1250 RPM: 1200 PHASE/HZ/VOLTS: 3/60/4160INSULATION/S.F.: F-VPI/1.15 ENCLOSURE: Class 1, Group D, Div 2 STARTER:J-C Across the Line Starter

-   -   INCLUDES: Class F Insulation, 1.15 S.F. with Class B rise at 1.0        S.F., 60 HZ, Non Sparking for Div. 2 area, 120 Volt Space        Heaters, 3300 ft elevation, 40 deg. C. ambient, Standard        Engineering Test. Space heaters will be terminated in the motor        starter or MCC. Stator and bearing RTD's are included

The first and second couplings 106 and 110 are MagnaGuard MagnaDrivemagnetic clutch couplings that incorporate an overrunning clutch intothe driven hub that mounts the motor shaft. In order to use the engineor turbine 108, the engine or turbine 108 is started allowed to warm upat idle speed. The engine or turbine 108 is then sped up to run speed.When the engine or turbine 108 speed becomes faster than themotor/generator 102 speed, the overrunning clutch engages and the engineor turbine 108 becomes the prime mover.

The applicable data for the cooler (not shown) is:

Manufacturer: AIR X CHANGERS Model: 132EH Fan Diameter: 132″ Fan TipSpeed: <12,000 FPM Design Max Working Temperature Sections PressureDegrees In/Out Louvers FJW 150 PSIG 195/168 Degrees TAW 150 PSIG 148/130Degrees AC 1100 PSIG  282/120 Degrees Manual Ambient Design 100° F.Temperature: Design Approach 200° F. Water surge tank complete withgauge glass, vent and fair cap. Service EJW/SLOW TAW/CLOW AC Flow 264GPM 90 GPM 14. OMMSCFD Fluid 50% GLY .50% GLY .65 SPGR Temperature in,195.0 147.8 282.0 ° F. Temperature out, 168.1 130.0 120.0 ° F. Pressure,PSI 960 PSIG Pressure Drop, 2.5 1.3 5.9 PSI Heat Load, 3333837 7150792975148 BTU/HR True MTD 59.0 30.3 52.8 Overall Rate 163.5 126.3 113.6Foulling Factor .0005 .0005 .0010 Tube Surface, 346 191 498 Sq. Ft.Total Surface, 5498 3032 7913 Sq. Ft. Sections, No. of COMBINED COMBINED1 Connected SINGLY SINGLY SINGLY No. Pieces 1 1 2 Design Temp., 300/−10300/10 350/10 ° F. Design Press., 150 150 1100 PSIG Totl Press., PSIG225 225 1650 Nozzles 6-150 RF 3-150 RF 6-600 RF Tubes, 5/8 × 16 5/8 × 165/8 × 16 OD × BWO Material SA214 STEEL SA214 STEEL SA214 STEELNo./Sect., 107, 20 59, 20 154, 20 Lgth., Ft. No. Rowes 3 3 4 FlangesSA105SCH 40 SA105SCH 40 SA105SCH 80 Fins. Type WHEEL WHEEL WHEELMaterial AL AL AL Headers, Type BOX BOX BOX Materials STEEL STEEL STEELPlugs, Type TAPER TAPER SHOULDER Material BRASS BRASS STEEL ASMF, CodeYES Stamp Total SCFM Temp. to ° F. Temp Out ° F. Elev. Ft. 177190 100136 1000

The applicable data for the cooler driver (not shown) is:

Manufacturer: ARROW SPECIALTY COMPANY Model: VRG 330 Configuration/No.of In-line 6 Cylinders: Combustion Type: Naturally Aspirated Bore XStroke: 3.875/4.665 Displacement (cu. inches): 330 Speed Range Min/Max:900/2200 Continuous BHP @ Mfg. 68 @ 1800 RPM Rating: 60 @ 1600 RPM 52 @1400 RPM 42 @ 1200 RPM Ignition System: Altronic V non Shielded ExhaustSystem: Engine Mounted Muffler Fuel Gas System: Block Valve, FuelShutoff and Vent Valve, Relief Valve, Pressure Regulators. StartingSystem: Air/Gas Starter with Strainer. Emissions: Nox 11.6, CO 14.6,NMHC 0.2

The applicable data for the scrubbers (not shown) are:

Process: Suction Diameter: 30 Sts: 60 Mawp: 635 Asme Code: Yes InternalDesign: Mesh Liquid Level Shutdown: MURPHY L1200 Liquid LevelController: MALLARD 3200 Liquid Level Dump Valve: MALLARD 5127 ReflexGauge Glass w/Cocks: Penberthy Or Equal Drain Piping: 1″ NPT

Relief valves for discharge and the fuel system are Mercer orEqual—Spring Operated. The relief valve exhaust is piped above cooler.Process piping is built in accordance with ANSI B31.3 Code. Suction andDischarge pulsation bottles are ASME Code Stamped. Scrubber andPulsation Bottle sizes and working pressures apply to typical designconditions.

The applicable data for the programmed logic controller (“PLC”) controlpanel is:

Qty Description Manufacturer Part Number 1 Chasis, 10-slot Allen Bradley1746-A10 1 Power Supply Module Allen Bradley 1748-P3 1 Processor Module,16k Allen Bradley 1747-L641 Mem, DH+ 1 EPROM, CPU Allen Bradley 1747-M111 Discrete, 24 V Sink, 16 Allen Bradley 1746-1B16 Input Module 1 Cable,Interface, Module, Entrelec 0027 816.17 16-channel Disctete In 1 Term,Interface, Module Entrelec 0031 025.05 16-channel Disctete In 1Discrete, 24 V Sink, Output Allen Bradley 1746-0816 Module 1 Cable,Interface, 16- Entrelec 0027 622.15 channel Disctete Out 1 Term,Interface, 16-channel Entrelec 0031 026.06 Discrete Out 1 Analog, 4-20mA, 6 in Allen Bradley 1745-N15 Module 1 Cable, Interface, Module,Entrelec 0034 702.25 S-channel Analog In 1 Term, Inteface, 8-channelEntrelec 0021 062.11 Analog In 1 Analog, 4-20 mA, 4 out Allen Bradley1746-NO41 Module 1 Cable, Interface, Module Entrelec 0027 804.244-channel Analog Out 1 Term, Interface, 4-channel Entrelec 0021 060.23Analog Out 1 Universal Analog Module, Spectrum 1748so-NIBu 8 channel 1CAT CCM Module Caterpillar 162-8734 1 CCM Cable Caterpillar 152-0453 1AB CCM Interface Module Mlille Omnii-Comm 3 Modular Cart Slot FillerAllen Bradley 1748-N2 1 PB, Rod Mushroom, “E8D” Allen Bradley800H-FRXTBAP 1 Sw, 2-pos Allen Bradley 800H-HR2D1P 1 PanelView 1000,AMBER, Allen Bradley 2711K10G8L1 24 Vdc, Keypad, DH+ 1 Power Supply, ACto 24 Viaar VI-PU33-EUU Vdc, 400 Watts 6 Fuse Block, Entrelec Entrelec00005918 5 Fuse, 6 amp, 3 AG Littlefuse 00005619 1 Fuse, 15 amp, 3 AGLittlefuse 00004709 50  Terminal Blcok, Entrelec, Entrelec 00003871 4End Section, Entrelec, Entrelec 00003872 8 End Stop, Entrelec, Entrelec00003873 1 F11, Acromag Phoenix 250T-FQ1-DT1 6 Relay, 4 PDT, CI Div11Square D 00006291 6 Relay, Socket Square D 00007488 1 Enclosure, 50 × 88w/Back FW Murphy Mfr 50225253 Panel 1 Base, Enclosure FW Murphy Mfr50225276 1 Speed Regulator FW Murphy Mfr 05704181 1 Speed Gauge FWMurphy Mfr 00006482 7 Speed Know FW Murphy Mfr 00005481

-   -   Analog Input/Outputs: Suction pressure—Rosemount Pressure        Transmitter        -   Discharge pressure—Rosemount Pressure Transmitter        -   Compressor lube oil filter differential pressure—Rosemount            Pressure Transmitter    -   RTD'S: Motor bearing and stator        -   Compressor discharge temperature—each cylinder        -   Compressor lube oil temperature    -   Discret Inputs:Compressor oil level low—KENCO LCE-10-FS        -   Engine oil level low—KENCO LCE-10-FS        -   High vibration—compressor—Murphy VS 2        -   High vibration—motor—Murphy VS 2        -   High vibration—cooler—Murphy VS 2        -   Lubricator no-flow—Whitlock DNFT-LED-PS

The skid 112 is a heavy duty oil field type with {fraction (3/16)}″checkered floor plate, four main runners and leveling jack screws. Skidmembers support all vessels and piping, and are provided with pipe endsfor skidding and lifting. The skid 112 will be concrete filled under theengine, compressor frame & distance pcs. The skid 112 also includes anenvironmental drip rail with four drain sumps. The skid 112 hasestimated package dimensions of fourteen feet (14′) wide by thirty-fivefeet (35′) long and an estimated weight of 125,000 lbs. The cooler hasestimated package dimensions of twenty-one feet (21′) wide by fifteenfeet (15′) long and an estimated weight of 20,000 lbs.

Now referring to FIG. 5, a block diagram of a redundant prime moversystem 650 in accordance with another embodiment of the presentinvention is shown. The redundant prime mover system 650 includes amotor/generator 652 coupled to a compressor 654 with a first coupling656 (also referred to as the “M/G-COMP Coupling”) and a engine orturbine 658 coupled to the compressor 654 with a second coupling 660(also referred to as the “E/T-COMP Coupling”). Couplings 656 and 660 canbe a clutch, magnetic coupling, gearbox or other suitable device toselectively engage/disengage the shaft of the compressor or pump 654.The engine 658 can be a variable speed engine. In one embodiment of thepresent invention, the engine 658 is oversized so that some amount ofelectricity can be generated using the motor/generator 652 even with thecompressor 654 is operating at peak load. In small to mediumapplications, the motor/generator 652, compressor 654 and engine orturbine 658 can be mounted on a skid (not shown) to form a package thatcan be transported and set up more quickly and economically thanindividually installing components 652, 654, 656, 658 and 660 in thefield. As will be appreciated by those skilled in the art, otherequipment (not shown), such as coolers, cooler drivers, scrubbers andapplication specific devices, may be connected to the motor/generator652, compressor 654 or engine 658.

The motor/generator 652 is electrically connected to an electricalnetwork connection 662, which is used as a source of electricity to runthe motor/generator 652 and drive the compressor 654 and a deliverypoint for the electricity generated by the motor/generator 652 when theengine 658 is supplying more output power than is required to drive thecompressor 654. The exact interface between the electrical networkconnection 662 and the transmission or distribution system 664 will varyfrom one installation to another. The electrical network connection 662may include some of the equipment described in FIG. 1, such asstep-down/step-up transformer, breaker or switches.

Although a compressor 654 is depicted, compressor 654 could also be apump or other machine that is driven by large engines, turbines ormotors. Input line 666 and output line 668 are connected to compressor654. As will be appreciated by those skilled in the art, the connectionof the lines 666 and 668 to the compressor 654 will also include variousvalves, regulators and other flow protection/regulation devices. Theselines 666 and 668 may be taps off of a pipeline, such as natural gas orother petroleum product, or part of a processing plant. If input line666 contains a product that can be used as fuel for the engine orturbine 658, a first fuel supply line 670 having a regulating valve 672will connect the input line 666 to the engine or turbine 658. In suchcases, first fuel supply line 670 will serve as the primary fuel supplyfor the engine or turbine 658. A second fuel supply line 674 having aregulating valve 676 will typically connect the engine or turbine 658 toan alternate fuel supply. If input line 666 does not contains a productthat can be used as fuel for the engine or turbine 658, second fuelsupply line 674 will be the primary source of fuel to the engine orturbine 658.

Referring now to FIG. 6, a block diagram of a redundant prime moversystem 700 in accordance with another embodiment of the presentinvention is shown. The redundant prime mover system 700 includes amotor/generator 702 coupled to a gearbox 704 with a first coupling 706(also referred to as the “M/G-COMP Coupling”), a compressor 708 coupledto the gearbox 704 with a third coupling 710 and a engine or turbine 712coupled to the gearbox 704 with a second coupling 714 (also referred toas the “E/T-COMP Coupling”). Couplings 706, 710 and 714 can be a clutch,magnetic coupling, gearbox or other suitable device to selectivelyengage/disengage the shaft of the motor/generator 702, compressor orpump 708 and engine or turbine 712. The engine 712 can be a variablespeed engine. In one embodiment of the present invention, the engine 712is oversized so that some amount of electricity can be generated usingthe motor/generator 702 even with the compressor 708 is operating atpeak load. In small to medium applications, the motor/generator 702,gearbox 704, compressor 708 and engine or turbine 712 can be mounted ona skid (not shown) form a package that can be transported and set upmore quickly and economically than individually installing components702, 704, 706, 708, 710, 712 and 714 in the field. As will beappreciated by those skilled in the art, other equipment (not shown),such as coolers, cooler drivers, scrubbers and application specificdevices, may be connected to the motor/generator 702, gearbox 704,compressor 708 and engine or turbine 712.

The motor/generator 702 is electrically connected to an electricalnetwork connection 716, which is used as a source of electricity to runthe motor/generator 702 and drive the compressor 708 and a deliverypoint for the electricity generated by the motor/generator 702 when theengine 714 is supplying more output power than is required to drive thecompressor 708. The exact interface between the electrical networkconnection 716 and the transmission or distribution system 718 will varyfrom one installation to another. The electrical network connection 716may include some of the equipment described in FIG. 1, such asstep-down/step-up transformer, breaker or switches.

Although a compressor 708 is depicted, compressor 708 could also be apump or other machine that is driven by large engines, turbines ormotors. Input line 720 and output line 722 are connected to compressor708. As will be appreciated by those skilled in the art, the connectionof the lines 720 and 722 to the compressor 708 will also include variousvalves, regulators and other flow protection/regulation devices. Theselines 720 and 722 may be taps off of a pipeline, such as natural gas orother petroleum product, or part of a processing plant. If input line720 contains a product that can be used as fuel for the engine orturbine 712, a first fuel supply line 724 having a regulating valve 726will connect the input line 720 to the engine or turbine 712. In suchcases, first fuel supply line 724 will serve as the primary fuel supplyfor the engine or turbine 712. A second fuel supply line 728 having aregulating valve 730 will typically connect the engine or turbine 712 toan alternate fuel supply. If input line 720 does not contains a productthat can be used as fuel for the engine or turbine 712, second fuelsupply line 728 will be the primary source of fuel to the engine orturbine 712.

Although preferred embodiments of the present invention have beendescribed in detail, it will be understood by those skilled in the artthat various modifications can be made therein without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

1. A method for controlling a motor/generator and an engine coupled to amachine, comprising the steps of: selecting a first operating mode, asecond operating mode or a third operating mode based on one or moreparameters; driving the machine with the engine whenever the firstoperating mode is selected; driving the machine with the motor/generatorwhenever the second operating mode is selected; driving the machine andthe motor/generator with the engine such that the motor/generatorgenerates electricity for delivery to an electrical network connectionwhenever the third operating mode is selected; and wherein the firstoperating mode is selected whenever a first estimated operational costfor the engine is less than an estimated operational cost for themotor/generator, the second operating mode is selected whenever anestimated operational cost for the motor/generator is less than or equalto the first estimated operational cost for the engine, and the thirdoperating mode is selected whenever a selling price for the electricityis greater than a second estimated operational cost for the engine. 2.The method as recited in claim 1, further comprising the step ofobtaining the one or more parameters.
 3. The method as recited in claim1, further comprising the step of monitoring the one or more parameters.4. The method as recited in claim 1, further comprising the step ofdetermining whether to change the selected operating mode based on oneor more changes in the one or more parameters.
 5. The method as recitedin claim 1, further comprising the step of storing the one or moreparameters.
 6. The method as recited in claim 1, wherein the machine isa compressor.
 7. The method as recited in claim 1, wherein the machineis a pump.
 8. The method as recited in claim 1, wherein the engine is aturbine.
 9. The method as recited in claim 1, wherein the engine is avariable speed engine.
 10. The method as recited in claim 1, wherein thestep of selecting a first operating mode, a second operating mode or athird operating mode based on one or more parameters comprises the stepof selecting a first operating mode, a second operating mode, a thirdoperating mode or a fourth operating mode based on one or moreparameters.
 11. The method as recited in claim 10, further comprisingthe step of driving the machine with both the engine and themotor/generator whenever the fourth operating mode is selected.
 12. Themethod as recited in claim 1, wherein the one or more parameters includean estimated operational cost for the engine.
 13. The method as recitedin claim 1, wherein the one or more parameters include an estimatedoperational cost for the motor/generator.
 14. The method as recited inclaim 1, wherein the one or more parameters include a selling price forelectricity.
 15. The method as recited in claim 1, wherein the one ormore parameters include a fuel cost for the engine.
 16. The method asrecited in claim 1, wherein the one or more parameters include anelectricity cost for the motor/generator.
 17. The method as recited inclaim 1, wherein the one or more parameters include a time period. 18.The method as recited in claim 1, wherein the one or more parametersinclude an emission limit.
 19. The method as recited in claim 1, whereinthe one or more parameters include an audible noise limit.
 20. A methodfor controlling a motor/generator and an engine coupled to a machine,comprising the steps of: selecting a first operating mode, a secondoperating mode, a third operating mode or a fourth operating mode basedon one or more parameters; driving the machine with the engine wheneverthe first operating mode is selected; driving the machine with themotor/generator whenever the second operating mode is selected; anddriving the machine with both the engine and the motor/generatorwhenever the third operating mode is selected; driving the machine andthe motor/generator with the engine such that the motor/generatorgenerates electricity for delivery to the electrical network connectionwhenever the fourth operating mode is selected; and wherein the firstoperating mode is selected whenever a first estimated operational costfor the engine is less than an estimated operational cost for themotor/generator, the second operating mode is selected whenever anestimated operational cost for the motor/generator is less than or equalto the first estimated operational cost for the engine, and the fourthoperating mode is selected whenever a selling price for the electricityis greater than a second estimated operational cost for the engine. 21.The method as recited in claim 20, further comprising the step ofobtaining the one or more parameters.
 22. The method as recited in claim20, further comprising the step of monitoring the one or moreparameters.
 23. The method as recited in claim 20, further comprisingthe step of determining whether to change the selected operating modebased on one or more changes in the one or more parameters.
 24. Themethod as recited in claim 20, further comprising the step of storingthe one or more parameters.
 25. The method as recited in claim 20,wherein the machine is a compressor.
 26. The method as recited in claim20, wherein the machine is a pump.
 27. The method as recited in claim20, wherein the engine is a turbine.
 28. The method as recited in claim20, wherein the engine is a variable speed engine.
 29. The method asrecited in claim 20, wherein the one or more parameters include anestimated operational cost for the engine.
 30. The method as recited inclaim 20, wherein the one or more parameters include an estimatedoperational cost for the motor/generator.
 31. The method as recited inclaim 20, wherein the one or more parameters include a selling price forelectricity.
 32. The method as recited in claim 20, wherein the one ormore parameters include a fuel cost for the engine.
 33. The method asrecited in claim 20, wherein the one or more parameters include anelectricity cost for the motor/generator.
 34. The method as recited inclaim 20, wherein the one or more parameters include a time period. 35.The method as recited in claim 20, wherein the one or more parametersinclude an emission limit.
 36. The method as recited in claim 20,wherein the one or more parameters include an audible noise limit. 37.An apparatus for controlling an engine and a motor/generator to drive amachine comprising: a processor; a memory communicably coupled to theprocessor; an engine control interface communicably coupled to theprocessor; a motor/generator control interface communicably coupled tothe processor; a remote interface communicably coupled to the processor;and wherein the processor selects a first operating mode, a secondoperating mode or a third operating mode based on one or moreparameters, the processor controls the engine via the engine controlinterface to drive the machine whenever the first operating mode isselected, the processor controls the motor/generator via themotor/generator control interface to drive the machine whenever thesecond operating mode is selected, and the processor controls the enginevia the engine control interface and the motor/generator via themotor/generator control interface to drive the machine themotor/generator with the engine such that the motor/generator generateselectricity for delivery to an electrical network connection wheneverthe third operating mode is selected.
 38. The apparatus as recited inclaim 37, further comprising an input/output interface communicablycoupled to the processor.
 39. The apparatus as recited in claim 38,further comprising one or more input/output devices communicably coupledto the input/output interface.
 40. The apparatus as recited in claim 38,further comprising one or more data storage devices communicably coupledto the input/output interface.
 41. The apparatus as recited in claim 37,further comprising a server communicably coupled to the remote interfacevia a network.
 42. The apparatus as recited in claim 37, furthercomprising a remote terminal communicably coupled to the remoteinterface via a network.
 43. The apparatus as recited in claim 37,further comprising a machine control interface communicably coupled tothe processor.
 44. The apparatus as recited in claim 37, wherein theprocessor obtains the one or more parameters.
 45. The apparatus asrecited in claim 37, wherein the processor monitors the one or moreparameters.
 46. The apparatus as recited in claim 37, wherein theprocessor determines whether to change the selected operating mode basedon one or more changes in the one or more parameters.
 47. The apparatusas recited in claim 37, wherein the processor stores the one or moreparameters in the memory.
 48. The apparatus as recited in claim 37,wherein the machine is a compressor.
 49. The apparatus as recited inclaim 37, wherein the machine is a pump.
 50. The apparatus as recited inclaim 37, wherein the engine is a turbine.
 51. The apparatus as recitedin claim 37, wherein the engine is a variable speed engine.
 52. Theapparatus as recited in claim 37, wherein the processor selects a firstoperating mode, a second operating mode, a third operating mode or afourth operating mode based on one or more parameters.
 53. The apparatusas recited in claim 52, wherein the processor controls the engine viathe engine control interface and the motor/generator via themotor/generator control interface to drive the machine with both theengine and the motor/generator whenever the fourth operating mode isselected.
 54. The apparatus as recited in claim 37, wherein the one ormore parameters include an estimated operational cost for the engine.55. The apparatus as recited in claim 37, wherein the one or moreparameters include an estimated operational cost for themotor/generator.
 56. The apparatus as recited in claim 37, wherein theone or more parameters include a selling price for electricity.
 57. Theapparatus as recited in claim 37, wherein the one or more parametersinclude a fuel cost for the engine.
 58. The apparatus as recited inclaim 37, wherein the one or more parameters include an electricity costfor the motor/generator.
 59. The apparatus as recited in claim 37,wherein the one or more parameters include a time period.
 60. Theapparatus as recited in claim 37, wherein the one or more parametersinclude an emission limit.
 61. The apparatus as recited in claim 37,wherein the one or more parameters include an audible noise limit. 62.The apparatus as recited in claim 37, wherein the first operating modeis selected whenever a first estimated operational cost for the engineis less than an estimated operational cost for the motor/generator, thesecond operating mode is selected whenever an estimated operational costfor the motor/generator is less than or equal to the first estimatedoperational cost for the engine, and the third operating mode isselected whenever a selling price for the electricity is greater than asecond estimated operational cost for the engine.
 63. An apparatus forcontrolling an engine and a motor/generator to drive a machinecomprising: a processor; a memory communicably coupled to the processor;an engine control interface communicably coupled to the processor; amotor/generator control interface communicably coupled to the processor;a remote interface communicably coupled to the processor; and whereinthe processor selects a first operating mode, second operating mode or athird operating made based on one or more parameters, the processorcontrols the engine via the engine control interface to drive themachine whenever the first operating mode is selected, the processorcontrols the motor/generator via the motor/generator control interfaceto drive the machine whenever the second operating mode is selected, andthe processor controls the engine via the engine control interface andthe motor/generator via the motor/generator control interface to drivethe machine with both the engine and the motor/generator whenever thethird operating mode is selected.
 64. The apparatus as recited in claim63, further comprising an input/output interface communicably coupled tothe processor.
 65. The apparatus as recited in claim 64, furthercomprising one or more input/output devices communicably coupled to theinput/output interface.
 66. The apparatus as recited in claim 64,further comprising one or more data storage devices communicably coupledto the input/output interface.
 67. The apparatus as recited in claim 63,further comprising a server communicably coupled to the remote interfacevia a network.
 68. The apparatus as recited in claim 63, furthercomprising a remote terminal communicably coupled to the remoteinterface via a network.
 69. The apparatus as recited in claim 63,further comprising a machine control interface communicably coupled tothe processor.
 70. The apparatus as recited in claim 63, wherein theprocessor obtains the one or more parameters.
 71. The apparatus asrecited in claim 63, wherein the processor monitors the one or moreparameters.
 72. The apparatus as recited in claim 63, wherein theprocessor determines whether to change the selected operating mode basedon one or more changes in the one or more parameters.
 73. The apparatusas recited in claim 63, wherein the processor stores the one or moreparameters in the memory.
 74. The apparatus as recited in claim 63,wherein the machine is a compressor.
 75. The apparatus as recited inclaim 63, wherein the machine is a pump.
 76. The apparatus as recited inclaim 63, wherein the engine is a turbine.
 77. The apparatus as recitedin claim 63, wherein the engine is a variable speed engine.
 78. Theapparatus as recited in claim 63, wherein the processor selects a firstoperating mode, a second operating mode, a third operating mode or afourth operating mode based on one or more parameters.
 79. The apparatusas recited in claim 78, wherein the processor controls the engine viathe engine control interface and the motor/generator via themotor/generator control interface to drive the machine and themotor/generator with the engine such that the motor/generator generateselectricity for delivery to an electrical network connection wheneverthe fourth operating mode is selected.
 80. The apparatus as recited inclaim 79, wherein the first operating mode is selected whenever a firstestimated operational cost for the engine is less than an estimatedoperational cost for the motor/generator, the second operating mode isselected whenever an estimated operational cost for the motor/generatoris less than or equal to the first estimated operational cost for theengine, and the fourth operating mode is selected whenever a sellingprice for the electricity is greater than a second estimated operationalcost for the engine.
 81. The apparatus as recited in claim 63, whereinthe one or more parameters include an estimated operational cost for theengine.
 82. The apparatus as recited in claim 63, wherein the one ormore parameters include an estimated operational cost for themotor/generator.
 83. The apparatus as recited in claim 63, wherein theone or more parameters include a selling price for electricity.
 84. Theapparatus as recited in claim 63, wherein the one or more parametersinclude a fuel cost for the engine.
 85. The apparatus as recited inclaim 63, wherein the one or more parameters include an electricity costfor the motor/generator.
 86. The apparatus as recited in claim 63,wherein the one or more parameters include a time period.
 87. Theapparatus as recited in claim 63, wherein the one or more parametersinclude an emission limit.
 88. The apparatus as recited in claim 63,wherein the one or more parameters include an audible noise limit.
 89. Acomputer program embodied on a computer readable medium for controllinga motor/generator and an engine coupled to a machine, the computerprogram comprising: a code segment for selecting a first operating mode,second operating mode or a third operating mode based on one or moreparameters; a code segment for driving the machine with the enginewhenever the first operating mode is selected; a code segment fordriving the machine with the motor/generator whenever the secondoperating mode is selected; a code segment for driving the machine andthe motor/generator with the engine such that the motor/generatorgenerates electricity for delivery to an electrical network connectionwhenever the third operating mode is selected; and wherein the firstoperating mode is selected whenever a first estimated operational costfor the engine is less than an estimated operational cost for themotor/generator, the second operating mode is selected whenever anestimated operational cost for the motor/generator is less than or equalto the first estimated operational cost for the engine, and the thirdoperating mode is selected whenever a selling price for the electricityis greater than a second estimated operational cost for the engine. 90.The computer program as recited in claim 89, further comprising a codesegment for obtaining the one or more parameters.
 91. The computerprogram as recited in claim 89, further comprising a code segment formonitoring the one or more parameters.
 92. The computer program asrecited in claim 89, further comprising a code segment for determiningwhether to change the selected operating mode based on one or morechanges in the one or more parameters.
 93. The computer program asrecited in claim 89, further comprising a code segment for storing theone or more parameters.
 94. The computer program as recited in claim 89,wherein the machine is a compressor.
 95. The computer program as recitedin claim 89, wherein the machine is a pump.
 96. The computer program asrecited in claim 89, wherein the engine is a turbine.
 97. The computerprogram as recited in claim 89, wherein the engine is a variable speedengine.
 98. The computer program as recited in claim 89, wherein thecode segment for selecting a first operating mode, a second operatingmode or a third operating mode based on one or more parameters comprisesa code segment for selecting a first operating mode, a second operatingmode, a third operating mode or a fourth operating mode based on one ormore parameters.
 99. The computer program as recited in claim 98,further comprising a code segment for driving the machine with both theengine and the motor/generator whenever the fourth operating mode isselected.
 100. The computer program as recited in claim 89, wherein theone or more parameters include an estimated operational cost for theengine.
 101. The computer program as recited in claim 89, wherein theone or more parameters include an estimated operational cost for themotor/generator.
 102. The computer program as recited in claim 89,wherein the one or more parameters include a selling price forelectricity.
 103. The computer program as recited in claim 89, whereinthe one or more parameters include a fuel cost for the engine.
 104. Thecomputer program as recited in claim 89, wherein the one or moreparameters include an electricity cost for the motor/generator.
 105. Thecomputer program as recited in claim 89, wherein the one or moreparameters include a time period.
 106. The computer program as recitedin claim 89, wherein the one or more parameters include an emissionlimit.
 107. The computer program as recited in claim 89, wherein the oneor more parameters include an audible noise limit.
 108. A computerprogram embodied on a computer readable medium for controlling amotor/generator and an engine coupled to a machine, wherein themotor/generator is connected to an external electrical networkconnection, the computer program comprising: a code segment forselecting a first operating mode, a second operating mode, a thirdoperating mode or a fourth operating mode based on one or moreparameters; a code segment for driving the machine with the enginewhenever the first operating mode is selected; a code segment fordriving the machine with the motor/generator whenever the secondoperating mode is selected; a code segment for driving the machine withboth the engine and the motor/generator whenever the third operatingmode is selected; a code segment for driving the machine and themotor/generator with the engine such that the motor/generator generateselectricity for delivery to the external electrical network connectionwhenever the fourth operating mode is selected; and wherein the firstoperating mode is selected whenever a first estimated operational costfor the engine is less than an estimated operational cost for themotor/generator, the second operating mode is selected whenever anestimated operational cost for the motor/generator is less than or equalto the first estimated operational cost for the engine, and the fourthoperating mode is selected whenever a selling price for the electricityis greater than a second estimated operational cost for the engine. 109.The computer program as recited in claim 108, further comprising a codesegment for obtaining the one or more parameters.
 110. The computerprogram as recited in claim 108, further comprising a code segment formonitoring the one or more parameters.
 111. The computer program asrecited in claim 108, further comprising a code segment for determiningwhether to change the selected operating mode based on one or morechanges in the one or more parameters.
 112. The computer program asrecited in claim 108, further comprising a code segment for storing theone or more parameters.
 113. The computer program as recited in claim108, wherein the machine is a compressor.
 114. The computer program asrecited in claim 108, wherein the machine is a pump.
 115. The computerprogram as recited in claim 108, wherein the engine is a turbine. 116.The computer program as recited in claim 108, wherein the engine is avariable speed engine.
 117. The computer program as recited in claim108, wherein the one or more parameters include an estimated operationalcost for the engine.
 118. The computer program as recited in claim 108,wherein the one or more parameters include an estimated operational costfor the motor/generator.
 119. The computer program as recited in claim108, wherein the one or more parameters include a selling price forelectricity.
 120. The computer program as recited in claim 108, whereinthe one or more parameters include a fuel cost for the engine.
 121. Thecomputer program as recited in claim 108, wherein the one or moreparameters include an electricity cost for the motor/generator.
 122. Thecomputer program as recited in claim 108, wherein the one or moreparameters include a time period.
 123. The computer program as recitedin claim 108, wherein the one or more parameters include an emissionlimit.